异常
MySQL8.0默认的SQL模式包含了ONLY_FULL_GROUP_BY，MySQL5.7默认的SQL模式也包含了ONLY_FULL_GROUP_BY，但是MySQL5.6是不包含的，有的项目从5.6升级到5.7的时候，把SQL模式中的ONLY_FULL_GROUP_BY去掉了，再升级到8.0时，可能会报下面的异常：
Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column
'java_test.student.subject' which is not functionally dependent on columns in GROUP BY
clause; this is incompatible with sql_mode=only_full_g
